Takedown firearm

Abstract

A takedown firearm that may utilize removable barrels of different calibers. The disclosed firearm does not require a barrel extension, instead providing positioning of the barrel that is sufficiently precise and repeatable. Tensioning of the barrel is provided passively during installation of the removable barrel, without need for adjustment or additional tightening. Securing the removable barrel to the receiver does not structurally involve the fore end, thereby avoiding harmonics effects associated with fore end interfaces to the receiver. The firearm takes advantage of an “underspaced” chamber arrangement to provide additional tolerance for manufacturing and assembly of the firearm.

What is claimed is: 
     
         1 . A takedown firearm, comprising:
 a receiver, including:
 a front receiver ring that includes a distal face and defines an inside diameter; 
 a locking stud that extends radially inward relative to said inside diameter; and 
 a detent plunger that extends radially inward relative to said inside diameter, said detent plunger and said locking stud being centered about a common plane, 
   a removable barrel defining a barrel axis and defining an outer dimension at a proximal end portion, said proximal end portion including a shank portion, wherein said shank portion:
 includes a proximal face and an outer surface that defines a shank diameter dimensioned for a close sliding fit with said inside diameter of said front receiver ring, said shank diameter being less than said outer dimension of said proximal end portion of said removable barrel to define a shoulder at a junction of said outer dimension and said shank portion; 
 includes a locking stud track configured to guide said locking stud axially and rotationally during assembly; 
 includes a plunger track configured to guide said detent plunger axially and rotationally during assembly; and 
 defines a detent notch at a rotational extremity of said plunger track, and 
   a tensioner assembly including a biasing element and a collar, said collar having a proximal face that defines and is concentric about a tensioner axis, said tensioner assembly defining a proximal opening and a distal opening, said proximal opening being greater than said shank diameter, said distal opening being configured to receive said outer dimension of said proximal end portion, said biasing element being disposed between said collar and said shoulder,   wherein said shank portion is insertable into said front receiver ring so that said locking stud track guides said locking stud and said plunger track guides said detent plunger to an interlocked configuration, and   wherein, in said interlocked configuration, said detent plunger is registered within said detent notch and said distal face of said front receiver ring registers against said proximal face of said collar to compress said biasing element.   
     
     
         2 . The takedown firearm of  claim 1 , wherein, when in said interlocked configuration, said locking stud registers against a locking face of said track to establish a locking stud offset from said locking stud to said proximal face of said shank portion. 
     
     
         3 . The takedown firearm of  claim 1 , wherein said locking stud track defines a cylindrical cam for guiding said locking stud in a tangential direction during assembly. 
     
     
         4 . The takedown firearm of  claim 3 , wherein said cylindrical cam defines a slope relative to a radial-tangential plane of said shank, said slope being in a range of 5 degrees to 20 degrees inclusive. 
     
     
         5 . The takedown firearm of  claim 4 , wherein said slope varies along a tangential length of said cylindrical cam within said range of 5 degrees to 20 degrees inclusive. 
     
     
         6 . A takedown firearm, comprising:
 a receiver ring that defines an inside diameter;   a locking stud that extends radially inward from said inside diameter of said receiver ring;   a removable barrel including a shank portion and a barrel body portion, said shank portion being insertable into said receiver ring and including a locking stud track configured to guide said removable barrel axially and rotationally over said locking stud during assembly; and   a tensioner assembly disposed between said barrel body portion and said receiver ring, said tensioner assembly including a biasing element,   wherein said shank portion is insertable into said receiver ring so that said locking stud track guides said locking stud to an interlocked configuration with said removable barrel, and   wherein, in said interlocked configuration, said tensioner assembly is disposed between said receiver ring and said barrel body portion to bias said removable barrel in a distal direction relative to said receiver ring.   
     
     
         7 . The takedown firearm of  claim 6 , comprising a detent plunger that extends radially inward from said inside diameter of said receiver ring, said shank portion including a plunger track configured to guide said detent plunger axially and rotationally during assembly. 
     
     
         8 . The takedown firearm of  claim 7 , wherein said shank portion defines a detent notch at a rotational extremity of said plunger track, wherein, in said interlocked configuration, said detent plunger is registered within said detent notch. 
     
     
         9 . The takedown firearm of  claim 7 , wherein said detent plunger and said locking stud are centered about a common plane. 
     
     
         10 . The takedown firearm of  claim 9 , wherein a barrel axis of said removable barrel is coplanar with said common plane. 
     
     
         11 . The takedown firearm of  claim 6 , wherein:
 said barrel body portion defines an outer dimension of said removable barrel;   said shank portion including a proximal face and an outer surface that defines a shank diameter dimensioned for a close sliding fit with said inside diameter of said receiver ring, said shank diameter being less than an outer dimension of said barrel body portion to define a shoulder at a junction of said outer dimension and said shank portion; and   said tensioner assembly is registered between and against said receiver ring and said barrel body portion to compress said biasing element for the biasing of said removable barrel in said distal direction.   
     
     
         12 . The takedown firearm of  claim 11 , wherein said tensioner assembly includes a collar having a proximal face that defines and is concentric about a tensioner axis, said tensioner assembly defining a proximal opening and a distal opening, said proximal opening being greater than said shank diameter, said distal opening being configured to receive said outer dimension of said barrel body portion at said junction, said biasing element being disposed between said collar and said shoulder of said removable barrel. 
     
     
         13 . A method for underspacing a chamber of a takedown firearm, comprising:
 identifying an ideal position of a chamber face of a takedown firearm that corresponds to the contact location of a bolt face when a bolt assembly is in a battery configuration;   fabricating a removable barrel to include a proximal face that, when said takedown firearm is in a fully interlocked configuration, establishes said chamber face; and   fabricating said removable barrel to position said proximal face of said removeable barrel proximal to said ideal position of said chamber face, thereby providing an underspaced chamber.   
     
     
         14 . The method of  claim 13 , comprising configuring said takedown firearm for delayed blowback operation, wherein a firing pin of said takedown firearm is not blocked because of said underspaced chamber. 
     
     
         15 . The method of  claim 13 , comprising configuring said takedown firearm for discharging rimfire ammunition. 
     
     
         16 . The method of  claim 13 , wherein said takedown firearm is manufactured so that a distance between said proximal face of said removable barrel and said ideal position of said chamber face does not exceed 12 mils. 
     
     
         17 . The method of  claim 13 , wherein the step of fabricating said removable barrel to position said proximal face includes:
 securing a locking stud to extend radially inward from an inside dimension of a receiver ring of said takedown firearm, said locking stud including a locking interface; and   forming a locking seat on said removable barrel to seat against said locking interface to position said proximal face of said removeable barrel for definition of said underspaced chamber.   
     
     
         18 . The method of  claim 17 , comprising:
 forming a flat on said locking stud to establish said locking interface; and   forming a flat on said locking seat for mating with said locking interface.   
     
     
         19 . The method of  claim 17 , comprising forming a locking stud track on said removeable barrel to rotationally guide said removeable barrel over said locking stud and into contact with said locking seat during assembly of said takedown firearm. 
     
     
         20 . The method of  claim 19 , comprising forming said locking stud track to axially guide said removeable barrel over said locking stud.